A unit for pumping air containing particles and separating the particles from the air is suitable to be used in a number of appliances, including a vacuum cleaner.
In general, in the field of vacuum cleaning, air is used as a medium to pick up dirt in the form of small particles, and to transport the particles to a particle storage space. When the air containing particles reaches the particle storage space, or before that time, the air and the particles need to be separated, such that only the particles stay behind in the space. Traditionally, filter bags are used in the separation process. However, the use of filter bags has some major drawbacks, including the fact that the airflow through the filter bag decreases over time due to an increased resistance of the filter bag which is the logical result of the increased number of particles that is absorbed by the filter bag. Furthermore, filter bags are space consuming, and provide a place for micro organisms to grow on, which is unhygienic.
Another type of separation process involves an application of the so-called cyclone principle. According to this principle, the air containing particles is blown at high speed into the particle storage space, in a direction tangential to the wall of the space, so that a vortex is realized. The dirt particles are made to move to the wall of the space under the influence of centrifugal force, and clean air from the center of the vortex is expelled from the space.
Yet another type of separation process involves an application of a so-called active cyclone, which is basically a kind of centrifugal fan in series with a fan as normally used in a vacuum cleaner or the like. The cyclone fan, which will hereinafter be referred to as separator fan, is placed such that during operation, it is counterproductive to the normal fan, wherein it wants to pump air in the opposite direction. The normal fan is designed such as to be capable of pumping harder than the separator fan, so that it is achieved that the normal fan pumps air through the separator fan. In the process, the air enters the separator fan at the outer circumference, and exits the separator fan at the center. Hence, the air entering the separator fan is pumped against the centrifugal forces in this fan. On the basis of the fact that dirt particles have a much higher mass density than air, and the fact that the air does not have enough grip on the particles to drag them against the centrifugal field, it is achieved that the particles cannot pass the centrifugal field. In the process, the particles are separated from the air.
Advantages of an active cyclone are that a very robust construction may be realized, which can be very small compared to other constructions for performing the separation process. Furthermore, the active cyclone has the same advantages as the common cyclone. Among other things, the resistance remains constant during use, so that a decrease of suction power over time does not occur, and there is no dirt issue with water in case the vacuum cleaning is used in a wet cleaning process, as the construction is continually dried under influence of centrifugal effects.
U.S. Pat. No. 5,902,386 discloses a separator assembly for use in a vacuum cleaner, wherein the vacuum cleaner is a liquid bath vacuum cleaner, comprising a liquid bath for trapping dirt particles. The separator assembly includes a separator which is a dome-shaped element having a number of slots, and a disc-like plate. During operation of the vacuum cleaner, a fan assembly of a blower assembly and the separator are rapidly rotated about a central axis. The blower assembly creates a strong suction force to draw air entrained with dirt particles in the vacuum cleaner, and into contact with the liquid bath. Particles that are not trapped by the liquid bath are drawn by the blower assembly towards the separator.
The separator operates to separate the dirt particles from the ingested air by centrifugal force generated as a result of its rapid, axial rotation. The particle-free air is then drawn through the slots of the separator, and eventually exhausted back into the ambient environment.
The space where the separator is present is separated from the space where the fan assembly of the blower assembly is present by a wall, so that the space where particles are present is separated from the space where only clean air is present. However, a gap is present between the fan-separator assembly and the separation wall in order to allow for the necessary rotational motion of the fan-separator assembly. Hence, a dirt leaking problem is introduced. The disc-like plate of the separator assembly plays a role in solving this problem. In particular, as the plate rotates along with the separator, a counter airflow is generated, which helps to prevent water droplets and dirt particles from bypassing the separator and entering inside the space where the fan assembly of the blower assembly is present, through the gap between the fan-separator assembly and the separation wall.